1. Field of the Invention
The present invention relates to a light extraction film and a light emitting device using the same, and more particularly, to a light extraction film with the integration of a micro-lens array (MLA) film and an optical film having scattering particles and a light emitting device using the same.
2. Description of the Prior Art
Organic light emitting device is a self emission device and has the properties of thin construction, low power consumption, fast response time and being flexible, thus it can be widely applied to illumination field.
With reference to FIG. 1, FIG. 1 is a schematic sectional view of a conventional organic light emitting device. As shown in FIG. 1, the conventional organic light emitting device 10 includes a transparent substrate 12, a transparent electrode layer 14, an organic light emitting layer 16 and a metal electrode 18. The transparent electrode layer 14 is disposed on the transparent substrate 12 and serves as the anode of the organic light emitting device 10. The organic light emitting layer 16 is disposed on the transparent electrode layer 14. The metal electrode 18 is disposed on the organic light emitting layer 16 for serving as the cathode of the organic light emitting device 10. The metal electrode 18 further serves as a reflection layer which reflects light toward the transparent substrate 12 to emit out from the device when the organic light emitting layer 16 generates light.
However, not all the light generated by the organic light emitting layer 16 can emit out from the transparent substrate 12. Generally, about 30 percent of the light generated by the organic light emitting layer 16 will be lost due to the surface plasmon resonance in the interface between the organic light emitting layer 16 and the metal electrode 18. In addition, the refractive indices of the organic light emitting layer 16 and the transparent electrode layer 14 are greater than that of the transparent substrate 12, such that the organic light emitting layer 16 and the transparent electrode layer 14 form an optical waveguide mode to confine the light to the organic light emitting layer 16 and the transparent electrode layer 14, causing a loss of about 30 percent of light. In addition, the refractive index of the transparent substrate 12 is greater than that of air that forms a substrate mode, thus total internal reflection easily occurs when light pass through the interface between the transparent substrate 12 and air, resulting in a loss of about 20 percent of light. As a result, only about 20 percent of light generated by a conventional organic light emitting layer 16 can be effectively utilized. If the light confined in the device can be extracted from the device, the light-emitting efficiency of the organic light emitting device will be effectively improved.